I've never had kalk bombing fail. A few tablespoons of kalk in a whiskey glass, mix in some tank water till you have sort of a watery oatmeal/paste. Then use a larger syringe, like the type for marinating meat, and then blast the buggers. The best part is that the aiptasia will close on itself, usually injesting some kalk paste, so it's a guaranteed kill. Then cover the hole on the LR the aiptasia was with some more kalk. It will stay put.
Just be careful with smaller tanks you don't do too much and throw pH off.